發(fā)布時(shí)間：2018-04-09 01:14

  本文選題：電子射野影像系統(tǒng)　切入點(diǎn)：非晶硅平板探測(cè)器　出處：《蘇州大學(xué)》2012年碩士論文

【摘要】：非晶硅電子射野影像系統(tǒng)（amorphous silicon electronic portal imaging device，a-Si EPID）是目前最先進(jìn)的射野影像工具，，其成像速度快、成像面積大、高分辨率、數(shù)字格式存儲(chǔ)、耐受高劑量照射、快速獲得二維平面劑量信息等優(yōu)點(diǎn)，在加速器照射野常規(guī)質(zhì)量控制的檢測(cè)和放射治療劑量學(xué)驗(yàn)證方面具有很大的優(yōu)勢(shì)。課題研究了a-Si EPID在加速器照射野常規(guī)質(zhì)量保證和二維劑量驗(yàn)證的應(yīng)用，使用C#語言研制了一套劑量驗(yàn)證系統(tǒng)軟件,在計(jì)算照射野平坦度、對(duì)稱性、半影、照 射野和光野一致性以及二維劑量驗(yàn)證中顯示出較高的實(shí)用性和較好的劑量精度。論文對(duì)非晶硅平板探測(cè)器的物理劑量學(xué)品質(zhì)進(jìn)行了研究，通過劑量刻度模式修正加速器均整器導(dǎo)致的射野不均勻性。將像素值轉(zhuǎn)換為相對(duì)劑量分布得到不同照射野下的離軸比曲線，計(jì)算不同射野的平坦度、對(duì)稱性和半影，并與三維水箱數(shù)據(jù)進(jìn)行比較，分析所用的劑量刻度模式的可行性；通過計(jì)算射野中心到50%劑量線的距離與膠片測(cè)量結(jié)果進(jìn)行比較，證明了a-Si EPID可以快速的用于照射野 和光野一致性驗(yàn)證。在實(shí)現(xiàn)影像連續(xù)采集的基礎(chǔ)上，對(duì)非晶硅平板探測(cè)器的劑量學(xué)特性進(jìn)行了研究，分析各種參數(shù)的實(shí)際意義和相關(guān)影響因素，如穩(wěn)定性、劑量線性、不同照射野大小的散射、幀時(shí)間、電容大小等。根據(jù)劑量線性響應(yīng)關(guān)系擬合出劑量響應(yīng)函數(shù)，將灰度圖轉(zhuǎn)化為射野劑量圖。通過引入內(nèi)散射校正模型，修正非晶硅平板探測(cè)器內(nèi)部散射影響，設(shè)置規(guī)則和不規(guī)則野進(jìn)行修正后的劑量驗(yàn)證實(shí)驗(yàn)。對(duì)TPS計(jì)劃的RT dose數(shù)據(jù)解析，讀取劑量圖像；使用C#語言實(shí)現(xiàn)了Gamma分析法、距離一致性分析法和相對(duì)劑量差異法三種劑量比較算法，為TPS計(jì)算劑量分布與a-Si EPID實(shí)際測(cè)量的劑量分布比較提供了一種評(píng)估工具。
[Abstract]:The amorphous silicon electronic portal imaging devicesis-a-Si EPIDs are the most advanced image-field imaging tools at present. They have the advantages of fast imaging speed, large imaging area, high resolution, digital format storage and high dose tolerance.It has great advantages in conventional quality control of accelerator irradiation field and dosimetry verification of radiotherapy because of the advantages of fast obtaining two-dimensional planar dose information.The application of a-Si EPID in conventional quality assurance and two-dimensional dose verification of accelerator irradiation field is studied. A dose verification system software is developed by using C # language. The software is used to calculate the flatness, symmetry, penumbra and radiography of the irradiation field.The consistency of the radiation field and the light field as well as the two dimensional dose verification show higher practicability and better dose accuracy.The physical dosimetry quality of amorphous silicon flat panel detector is studied in this paper. The field heterogeneity caused by the accelerator homogenizer is corrected by the dose calibration mode.The off-axis ratio curves of different radiation fields are obtained by converting the pixel values into the relative dose distribution. The flatness, symmetry and penumbra of different radiation fields are calculated, and the feasibility of the dose calibration model is analyzed by comparing with the three-dimensional water tank data.By calculating the distance from the center of the field to the 50% dose line and comparing with the result of film measurement, it is proved that a-Si EPID can be used in the field of irradiation quickly.And field consistency verification.On the basis of continuous image acquisition, the dosimetric characteristics of amorphous silicon flat panel detector are studied. The practical significance of various parameters and related influencing factors, such as stability, dose linearity, scattering of different radiation fields, are analyzed.Frame time, capacitance size, etc.According to the dose linear response relation, the dose response function was fitted, and the gray scale image was transformed into the field dose map.By introducing the internal scattering correction model, the internal scattering effect of amorphous silicon flat detector is corrected, and the modified dose verification experiment is carried out by setting rules and irregular fields.The RT dose data of TPS program are analyzed and the dose images are read. Three dose comparison algorithms, Gamma analysis, distance consistency analysis and relative dose difference method, are implemented in C # language.This paper provides an evaluation tool for the comparison between the calculated dose distribution of TPS and the dose distribution measured by a-Si EPID.
【學(xué)位授予單位】：蘇州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2012
【分類號(hào)】：TH774

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本文編號(hào)：1724184